1. Field of the Invention
The present invention relates to vehicle seats, and more particularly to vehicle seats having seat back reclining mechanisms. More specifically, the present invention pertains to seat back reclining angle adjusting means for vehicle seats.
2. Description of the Prior Art
In Japanese utility model publication No. 58-1255, there is disclosed a vehicle seat having a seat back reclining mechanism which can provide a stepless adjustment of seat back reclining angle. The mechanism disclosed by the Japanese utility model includes an upper arm secured to the seat back and a lower arm secured to the seat cushion, the upper and lower arms being connected together through a speed reduction gear mechanism so that the upper arm can be inclined with respect to the lower arm through an actuation of the gear mechanism to obtain a desired reclining angle of the seat back. The speed reduction gear mechanism includes an internal gear provided on the upper arm and an external gear provided on the lower arm for meshing engagement with the internal gear. The external gear has teeth which are fewer than the number of teeth of the internal gear. The external gear also is carried by an eccentric shaft in an offset relation with respect to the internal gear. It is therefore possible to adjust steplessly tbe inclination angle of the upper arm with respect to the lower arm through a rotation of the eccentric shaft.
In this type of mechanism, the actuating knob is provided on the eccentric shaft so that it is located at a rearward side of the seat cushion. However, this particular location of the actuating knob is inconvenient to operate. It should further be noted that, in this type of conventional mechanism, the parts are held in the adjusted position under the frictional forces between teeth of the internal and external gears and between the eccentric shaft and bearing surfaces in the gears. In order to prevent the seat back from collapsing under the load of the passenger, it is required to provide suiiiciently high frictional forces, which will in turn require a high operating force.